All modern dental units have a water supply that provides coolant and rinse water to the dynamic dental instruments including the high-speed handpiece, air/water syringe and ultrasonic scaler. This water supply is connected to a domestic water system. Microbiological studies of this water supply revealed that the water is contaminated by water organisms and oral flora. These organisms have been found to be massive in number and some identified as pathogenic. Dental researchists have stated that this contamination could cause infection in immuno-suppressed patients, and cross infection may occur between dental patients.
Clinical tests show that oral flora is aspirated from a patient's oral cavity into the dental unit water lumens through the dynamic dental instruments. This revelation has prompted the Centers of Disease Control to recommend a 20 to 30 second purge of these instruments between each patient appointment. The American Dental Association and The American National Standards Institute developed Specification Number 47, dated Apr. 12, 1984, as the manufacturing criterion for dental unit manufacturers. This specification requires that a means be incorported in the dental unit to prevent water from being drawn back beyond the point of the dental instrument connection. These are attempts to improve the quality of water used for dental treatment. However, continuing research indicates that neither has significatly reduced contamination.
Medical studies have determined that disease incubation periods vary. Because of this variance it is difficult to make accurate assessments as to the time and place of infection. Dental treatment is frequently subgingival and invasive of the mucosa therefore providing a direct access to the vascular system. It is therefore prudent to use microbiologically pure water for cooling and rinsing during dental treatment in lieu of water considered by public health standards to be polluted and nonpotable.